The present invention is related to methods and devices used to determine the specific gravity or density of material specimens by water displacement methods. This invention is particularly suitable for use with material specimens which exhibit irregular or coarse exterior surfaces and porosity or voids, such as samples of uncompacted, loose, or compacted bituminous mixtures, soil samples, aggregates, and concrete specimens used in the structure, infrastructure, and/or underlayment of many roadways.
In the construction industry, a water displacement test is used to establish the material density associated with the acceptability of the material durability used to form the pavement or underlayment of roadways or other construction or building projects. For example, most roadways consist of a plurality of materials and layers including different types of aggregates, rocks, stones, gravel, or other materials which are compacted together to form the foundation and/or structure for the roadway surface and construction structures. These material compositions can be described as xe2x80x9ccompacted mixturesxe2x80x9d. The composition of the compacted mixture is generally considered to be an important factor in the service life of the construction project. In order to assure that the construction projects (such as a particular roadway or substructure) exhibit sufficient performance characteristics and useful service lives, most construction projects are constructed to certain minimum build specifications or standards. One important standard used to assess the acceptability of the compacted mixture, particularly in the asphalt and soil industries, is a bulk specific gravity and density measurement of the compacted mixture.
A typical standard test method used to assess the bulk density of the compacted bituminous (asphalt) mixture is ASTM D2726. During evaluation, a field sample or laboratory molded sample is obtained. The pavement specimens are usually taken from pavements in the field with a core drill, diamond or a carborundum saw, and the like. In any event, the core specimen, whether from the field or molded in the laboratory, is typically in the shape of a cylinder. As such, the field specimen typically exhibits a rough uneven exterior surface. In order to preserve the integrity of the core specimen during and after removal from pavements or molds (and during testing), care is taken to avoid distortion, bending, or cracking of the specimens.
Generally described, the ASTM D2726 test method involves measuring the specimen""s weight, both in air and in water. More particularly, during this analysis, three different weights of the specimen are measured; a weight in water, a dry weight, and a saturated surface dry weight. The difference between the sample""s weight in the air and in the water is equal to the weight of the water displaced (which can be measured, this determines the volume of the water displaced) and saturated surface dry weight can be used to ascertain the amount of water absorbed by the sample. Since the volume of displaced water is known, the specific gravity of the sample can be determined. The test method results can be used to determine the unit weight of compacted construction material (typically dense) mixtures. This method is generally accepted as being accurate for smooth and/or non-porous samples. Indeed, the method is used around the world to determine the conformance to various regulatory specifications, both for prepared laboratory samples and field extracted samples.
The ASTM D2726 test method is not recommended for use with samples that contain open or interconnecting voids or that absorb more than 2% of water by volume, or both, as determined by saturated surface dry weight, e.g., xe2x80x9cporous samplesxe2x80x9d. Using this test method for porous samples can provide unreliable density measurements. This is attributed to the variable amount of water absorbed by the porous sample which can result in an inaccurate volume determination and, thus, an inaccurate and unreliable density determination.
Presently, specification standards require that the porous samples be measured differently from the ASTM D2726 test method. Typically, ASTM D1188 is recommended for use if the percent water absorbed by the specimen or sample exceeds 2%. ASTM D1188 is directed to the use of xe2x80x9cparaffin-coated specimensxe2x80x9d to seal the sample to prevent water infiltration into the porous samples whose specific gravity is to be determined by water displacement methods. In one paraffin application, in order to coat the sample, the sample is submerged into hot-melted paraffin wax and pulled out and cooled allowing the paraffin to solidify and form a shell around the sample. The density is then determined using the water displacement method. Unfortunately, the thickness of the paraffin layer can be inconsistent, which can produce variability in the measurement results. Further, penetration of the wax into the voids themselves can result in inflated density measurements. In addition, paraffin wax is difficult, if not impossible, to completely remove once applied, and the specimen is generally rendered unsuitable for further analysis. Further, the presence of a supply of melted hot wax can introduce safety hazards for laboratory personnel.
ASTM D1188 describes using Parafilm(copyright), an elastomeric self-sealing moisture proof film obtainable from most scientific suppliers. As described, three pieces of Parafilm(copyright) are cut from the roll, two 100xc3x97100 mm (4xc3x974 in) and one 100xc3x97200 mm (4xc3x978 in). The backing is pulled off the backside of one of the 100xc3x97100 pieces and opposite sides of the film are grasped to stretch the film (carefully, without creating holes) and then placing the stretched film over one end of the specimen and pressing the sides of the stretched film around the sample. The specimen is turned over and positioned on a cushioned foam mat and the other end is wrapped with another piece of the stretched Parafilm(copyright). Another specimen is used to force the air pockets from both surfaces by pressing against a piece of foam which is positioned on top of the wrapped specimen. A sharp knife is used to trim the excess film, keeping a minimum of 15 mm (0.5 in) on the side of the specimen at each end. The third piece of film is then applied. This elastomeric film method determines the xe2x80x9capparent specific gravity of Parafilm(copyright)xe2x80x9d by using the specific gravity of an aluminum calibration cylinder before and after it is wrapped with Parafilm(copyright) as noted above. Unfortunately, this sealing method is relatively labor intensive. Further, the amount of Parafilm(copyright) used during the wrap as well as how it is stretched over the sample can be inconsistent, which can result in measurement inconsistencies. In addition, air can be trapped under the film during the film wrapping process. Still further, the film is susceptible to puncture both during application and during actual testing potentially allowing water to enter through the puncture. Clearly, either the trapped air or puncture can adversely affect the reliability of this method.
Another method for measuring the bituminous mix density by water displacement with coated specimens is proposed by Jack E. Stephens, in a report entitled xe2x80x9cBituminous Mix Density by Coated Specimen,xe2x80x9d Project Number 67-5, Connecticut Department of Transportation (January 1973). This method proposes using a vacuum pump and two sheets of acetate to wrap the specimen. The first acetate or plastic sheet is apparently heated and held in tension in position while the sample is raised until it contacts the plastic. The rising specimen enters the center of the tensioned sheet and forces the plastic to wrap around the upper surface and the sides of the specimen. The tensioned material provides a surplus of material extending from both sides when the first sheet is released from the tensioning members (plastic clamps). This surplus material is then trimmed, leaving the lower surface and a minor portion of the sides exposed. The sample is then turned such that the lower surface faces upward and a second sheet of acetate is wrapped over the remaining exposed surface, and the second sheet overlaps a portion of the first sheet along the sides. Again, the excess material of the second acetate sheet is trimmed. After trimming, the sample is enclosed in a shrink-wrap acetate material layer with a double layer of the acetate formed along its sides. This method also proposes using a heater when forming the plastic over the specimen, to soften the plastic to facilitate the molding of the (heated) soft plastic to the sample. Unfortunately the heating temperature and time of the plastic can affect the degree of the softness of the plastic, which, in turn, affects the adherence of the plastic to coarse, irregular, and porous samples, thereby undesirably introducing variations into the measurement. Again, this procedure can be relatively cumbersome and the amount of trim removed can vary from sample to sample, introducing possible measurement error. Further, without careful control of the amount of vacuum pulled on the sample, significant variability can occur in the density measurement. Also, the speed at which the sample is raised to contact the plastic can cause the specimen or sample to puncture the sealing material allowing water to leak into the sample during liquid displacement testing. In addition, asphalt softens at approximately 150xc2x0 F. Heating the plastic can soften the asphalt layer at the surface and thereby change or alter the composition or condition of the sample during the water displacement test and also for any subsequent tests conducted subsequent to the liquid displacement density determination.
In recent years, the Federal Highway Administration (xe2x80x9cFHAxe2x80x9d) has worked to improve the service life of bituminous pavements. As a result of a recent 5-year test, the FHA has recommended using compacted bituminous mixtures with larger aggregate size proportions. This larger aggregate size is believed to improve pavement performance and service life. Unfortunately, due to the use of larger aggregates, the asphalt specimens now prepared in the lab or extracted from the field have coarse and porous compositions. Typically, the coarse and porous compositions include a larger than 2% variation in air weight compared to saturated surface dry weight. However, the true absorption rate into the material is not possible with porous samples. The rapid water infiltration into the sample when placed in the tank and water drainage out of the sample after removal from the tank can mask the xe2x80x9ctruexe2x80x9d absorption rate and, adversely influence the density measurement results. This variation will make these samples unsuitable for the unsealed evaluation, potentially requiring that such samples be evaluated by sealed water displacement methods.
An additional test, known by those in the art as the xe2x80x9cRice Testxe2x80x9d or the xe2x80x9cRice Gravity Testxe2x80x9d, has conventionally been used to determine the maximum theoretical specific gravity of a loose (uncompacted) sample of asphalt or bituminous paving mixtures. This value is used to establish the intrinsic properties of the composition of the paving mixture which varies sample to sample depending, inter alia, on the types and amounts of aggregates and/or bituminous materials used therein. This pre-compacted theoretical specific gravity value can be used to evaluate the suitability of the mixture, and can also be used to analyze the subsequent compacted bituminous material to determine if the proper mix design compaction level is obtained.
Generally described, in the Rice Test method, one first positions the loose uncompacted bituminous sample in a flask. The flask is then filled with water to a predetermined level sufficient to cover the sample. A vacuum is then applied to the flask to attempt to remove all the air from the pores of the aggregate and/or other materials in the sample. Typically, after about 15 minutes, the flask is submerged and evaluated by the amount of water displaced inside a water tank. The water displacement test uses the known air weight and the evacuated weight of the sample undergoing analysis to calculate the sample maximum specific gravity. See e.g., ASTM D2041. This procedure generally takes about 20-30 minutes.
Unfortunately, the Rice method can cause performance problems with the associated vacuum systems. The performance of the vacuum systems degrade because, during the evacuation procedure, water from the flask can enter the pump and reduce its operating life. In addition, with more absorptive aggregates, water can be drawn into the pores of the components of the uncompacted mixture more readily during the initial 15 minutes of vacuum operation masking the true measurement. Unfortunately, a relatively lengthy correction test for water absorption must then be performed to compensate for the measurement errors attributed thereto. This correction test method can take 2-3 hours. In addition, in operation, the vacuum level introduced onto the sample undergoing analysis is very important to the test measurements. However, due to the performance degradation of the pump, the vacuum level introduced onto the sample can change with time, potentially causing repeatability problems with the tests.
It is therefore an object of the present invention to provide a reliable and easy to use method for determining the specific gravity and/or density of uncompacted and/or compacted material samples with water displacement evaluation techniques.
It is another object of the present invention to provide an improved method and device for sealing material specimens, including those exhibiting coarse surfaces and porous properties, to inhibit water infiltration into the sample when measuring specific gravity of that sample by water displacement methods.
It is an additional object of the present invention to provide a consistent and repeatable sealing method which minimizes laboratory labor efforts and can be easily used.
It is yet another object of the present invention to seal porous samples for water displacement evaluation in a manner which is relatively quick, provides accurate testing measurements, and which preserves the integrity of the sample such that it is suitable for further post-sealing test evaluation.
It is another object of the present invention to provide a reliable and easily used method for determining the maximum specific gravity and/or density of uncompacted or loose bituminous material samples with water displacement evaluation techniques.
It is an additional object of the present invention to provide a water displacement maximum specific gravity and/or permeability test method which reduces the likelihood that water will be drawn into the vacuum pump during testing procedures.
It is another object of the present invention to provide an easy method of transferring a sample undergoing evaluation from a vacuum apparatus to a testing apparatus while the sample is maintained within a sealant material in an evacuated state.
It is yet another object of the present invention to provide an evaluation method for assessing the permeability or porosity of asphalt.
It is an additional object of the present invention to provide a vacuum apparatus configured to reduce the likelihood that the bag will puncture during the sealing process.
It is another object of the present invention to provide improved methods of establishing apparent bag density values suitable for use in measurements employing water displacement tests.
It is yet another object of the present invention to provide improved reference samples and/or reference standard configurations for use in density measurements.
It is an additional object of the present invention to provide vacuum sealing systems and methods which handle samples for maximum density testing that can reduce errors which can be introduced by operational variation in vacuum pumps and/or vibration equipment used for conventional Rice Test evaluations.
These and other objects of the present invention are provided by methods, encased samples, and systems which employ at least one preformed precision-manufactured sealable bag which is sized and configured to hold a compacted material sample therein. The preformed resilient bags are manufactured to be consistent in size (or sizes), and, thus, are configured to reliably displace a constant volume of water, without relying on an operator""s shaping of the material onto the sample. The method and encased samples provide predictability in the sealing application and thus, more reliable water displacement measurement evaluations. During operation, the material specimen sample is conveniently inserted into the bag at the use point and the bag is then conformed to rest against the surface of the sample in a controlled manner, i. e., such as by manipulating the bag to a surface conformal configuration (the walls of the bag substantially conform to the sample""s external perimeter surface profile) and sealed. Preferably, a vacuum apparatus with a preset time and/or pressure is used to collapse or deflate a chamber holding the bag (remove the excess air) and then the chamber is also preferably controllably exhausted (returned to atmospheric pressure) in a manner which gradually introduces the air therein to collapse the bag against the sample and, thus, provides an automatic and consistent sealed sample configuration corresponding to the sample type. The controlled exhaust rate can inhibit punctures as the bag walls conform to the side of the specimen gradually (as opposed to abruptly). Advantageously, no trimming of excess material is required and the variability due to operator input is minimized. Also, after the water displacement test, the sample""s composition and structural integrity remains intact and the sample is thus available for further evaluation.
More particularly, a first aspect of the present invention is a sample specimen configuration for a dense material sample to inhibit liquid contacting the sample during liquid displacement tests. The sample specimen configuration comprises at least one preformed resilient bag having at least one sealed side and one opening formed therein and defining a holding chamber. The system also includes a material sample having an exterior surface contour positioned in the chamber of the preformed resilient bag. The preformed bag has a first non-sealed configuration and a second sealed configuration. In the second sealed configuration, the preformed bag is configured to substantially conform to the sample""s exterior surface contour. In a preferred embodiment, the configuration is provided by a system which includes a vacuum apparatus used to encase and conform the bag to the surface of the sample and a heater element used to seal the open edge of the bag while the bag is under vacuum.
Another aspect of the present invention is a method for preparing a compacted sample for liquid displacement testing. The method comprises the steps of providing a preformed resilient bag with predetermined dimensions, the bag having a perimeter with a portion of the perimeter having an open portion formed therein. A material specimen is subsequently inserted into the bag and the bag open portion is sealed. The method also includes the step of encasing the material specimen within the bag such that a portion of the bag substantially conforms the exterior profile of the material specimen held therein to thereby form an encased specimen suitable for liquid displacement evaluation.
An additional aspect of the present invention is an apparatus for sealing a specimen. The apparatus comprises a preformed resilient bag defining a holding chamber therein and a compacted material sample having an exterior surface contour positioned in the chamber of the resilient bag. The bag has a first non-sealed configuration and a second sealed configuration. In the second configuration, the bag is configured to encase and substantially conform about the sample""s exterior surface contour. The apparatus also includes a vacuum apparatus which is operably associated with the preformed bag holding the compacted material sample. In a preferred embodiment, the apparatus includes an air chamber with an air flow channel with an adjustable flow rate. In operation, and the bag collapses to conform to the exterior contour responsive to the controlled introduction of air into the air chamber after evacuation of same.
An additional aspect of the present invention is a reproducible puncture resistant water jacket for a compacted material specimen for use in water displacement density or specific gravity tests. The water jacket includes a preformed resilient bag structure having at least two co-joined sides. The structure is sized and configured to receive a compacted material specimen therein. As such, the bag structure has a first open configuration and a second sealed configuration. The bag structure core is conformal to the profile of the specimen in the second sealed configuration (i.e., a portion of the bag conforms to rest against the exterior of the specimen while the portions of the bag structure away from the specimen contacts the opposing wall surface). The bag structure is produced at a first site and completely sealed at a second site remote from the first site. Preferably, the bag structure is defined by a preformed bag with a single open side. It is also preferred that the bag structure be configured for puncture resistance such as with reinforcement regions, patches, or double bags.
Yet another aspect of the present invention is directed to a method for immersing a compacted mixture in a liquid displacement bath for determining the specific gravity of specimens. The method comprises the steps of inserting a material specimen having an exterior surface into a bag having at least one open side and encasing the specimen by collapsing a portion of the bag to substantially conform to the material specimen exterior surface. The method also includes sealing the bag to enclose the material specimen therein and placing the sealed collapsed bag with specimen in a liquid displacement bath. The volume of displaced water associated with the placing step is then measured. Preferably, the method also includes the step of establishing bag density values associated with a particular bag type and specimen type across a plurality of specimen thicknesses. This establishing step can be performed by using a plurality of reference standards with known densities (aluminum blocks) and different thicknesses to determine a mathematical model or relationship which can be programmed into a computer. This established relationship can be provided at the factory and not require an operator to determine the value at the point of test for each specimen in the laboratory.
An additional aspect of the present invention is a resilient container for a porous sample. The resilient container comprises a first layer of a first material. The first layer includes a first perimeter portion. The resilient container also includes a second layer of a second material configured to overlay the first layer. The second layer includes a second perimeter portion corresponding to the first perimeter portion. The first and second perimeter portions are co-joined along a major portion thereof defining an internal compressible chamber therebetween and edge portions which extend laterally outward from the chamber. A compacted material specimen is held in the chamber. The first and second layers are formed of a resilient material such that the chamber has a first collapsed position and a second non-collapsed position, the collapsed position corresponds to the chamber being sealed with the compacted material specimen positioned therein. Preferably, the first and second layer materials are selected to provide oxygen resistant shielding and/or puncture resistance.
Another aspect of the present invention is a method of preparing a porous sample for use in a water displacement testing. The method comprises the steps of inserting a porous sample having an exterior profile into a preformed bag and collapsing the preformed bag to contact the exterior profile of the porous sample. The preformed bag is sealed to enclose the porous sample therein, thereby providing a sealed sample.
Yet an additional aspect of the present invention is directed to a method and computer program product for sealing a material specimen in a preformed bag. The computer program product comprises a computer readable storage medium having computer readable program code means embodied in the medium, the computer-readable program code means comprises computer readable program code means for accepting user input information associated with identifying the material specimen and computer readable program code means for comparing the identified material specimen with predetermined operating parameters for directing the operation of a vacuum apparatus operably associated with the preformed bag holding the material specimen. The product also includes a computer readable program code means for directing the operation of the vacuum apparatus corresponding to the operating parameters associated with the identified material specimen to compress the preformed bag to substantially conform to the exterior shape of the material specimen. Preferably, the computer program product also includes a computer readable program code means for accepting user input information associated with the identification of the preformed bag being sealed (i.e., product identification number which relates to bag design parameters such as size, material type, etc.). In a preferred embodiment, the computer program product further includes a computer readable program code means for providing a preformed bag adjustment number for use in specific gravity or density measurement calculations associated with water displacement tests and a computer readable program code means for printing information to a printer.
It is an additional aspect of the present invention to provide a semi automated system for establishing specific gravity in compacted specimens using liquid displacement testing. The system includes a vacuum apparatus with an internal vacuum chamber and a first scale positioned integral to the vacuum apparatus such that it can provide a dry weight measure of a sealed specimen held therein. The system also includes a liquid displacement bath and a second scale operably associated with the liquid displacement bath. The system further includes a computer means operably associated with the first scale, the second scale, and the vacuum apparatus. The computer means includes a computer program product which has a computer readable program code means for calculating the specific gravity of a compacted material specimen corresponding to data directly input into the computer means from the first and second scales.
An additional aspect of the invention is directed to an alternative Rice Test evaluation. These methods analyze the density of a paving mixture or an uncompacted or loose material sample. The methods include the steps of measuring the weight of an uncompacted material sample in air and encasing the uncompacted material sample in a vacuum-sealed bag such that the bag substantially conforms to the material sample held therein. The weight of the sealed bag with the material sample held therein is weighed in air. The sealed bag with the material sample is then immersed in a liquid displacement bath. An opening is introduced or inserted into the sealed bag with the material sample as the material sample in the bag is immersed in the liquid displacement bath. The weight of the opened bag in liquid is measured subsequent to the forming step while the sample (in the bag) is immersed in the liquid displacement bath. The weight is obtained after water substantially fills the voids of the sample within the bag. The density of the uncompacted material sample is determined based on the weights obtained during the measuring steps.
In a preferred embodiment, the sealed bag with the sample therein is submerged completely in the liquid displacement bath and the scales are allowed to stabilize before the immersed bag is cut open. If holes have been introduced prior to this step (sometimes occurring because the specimens are coarse and can puncture the bag during handling), the scales will not stabilize during the first 120-240 seconds as water is seeping into the bag. If the scales stabilize during the first two minutes or so, this affirms that the integrity of the bag is maintained and the procedure can continue. If, on the other hand, the water immersion scales fail to stabilize, a leak in the bag is indicated. The non-stabilized scales can alert the operator to abort the test and reinitiate the test with a new sealed bag (with the specimen dried), or risk compromised data.
Preferably, the method also includes the step of distributing the uncompacted sample within the bag prior to the second measuring step (during the encasing step) such that the material sample is substantially uniformly spread across a major portion of the bag. In one embodiment, the loose mixture is held in a sub-container which is itself held encased and sealed in the bag. The sub-container is configured to allow water to enter during the immersion step after the opening is introduced in the bag or after the seal integrity is destroyed. The method can result in the calculation of the maximum theoretical specific gravity based on the sub-container and bag density value determined during the density determination step.
Another aspect of the present invention is a method for analyzing the density of a bituminous paving mixture comprising one or more of an uncompacted or loose material sample. The method includes the steps of inserting the bituminous paving mixture material sample into a sub-container having at least one aperture formed therein and encasing the paving mixture material sample in a sealant such that the sealant substantially conforms to the sub-container with the material sample held therein. The encased sub-container is then immersed with the paving mixture material sample held therein in a liquid displacement bath. An opening is introduced into the sealant and liquid from the liquid displacement bath is allowed to enter the sub-container and contact the paving mixture material sample held therein as the sub-container with the paving mixture material sample is immersed in the liquid displacement bath. The weight of the opened sealant with the sub-container and the paving mixture material sample while immersed in the liquid displacement bath is obtained subsequent to the introducing step and the density of the paving mixture material sample is determined.
In a preferred embodiment, the sealant is a bag and the material sample comprises uncompacted bituminous materials and/or loose aggregates and/or asphalt mixture.
It is yet another aspect of the invention to provide a method of evaluating the density of material specimens using a liquid displacement bath. The method includes the steps of: encasing a material specimen in a conformable sealant material; evacuating the encased material specimen; and immersing the encased material specimen in a liquid displacement bath while the encased material specimen is held in an evacuated state within the sealant material.
In a preferred embodiment, the conformable sealant material is a bag. It is also preferred, particularly for material specimens comprising uncompacted paving mixtures or loose aggregates, that the method also include the step of inserting the (loose) material specimen into a sub-container prior to the encasing step; the sub-container is configured and sized to hold the material specimen therein and/or to reduce compaction of the loose sample by the sealant""s contact with the material specimen.
Another aspect of the present invention is a sealable, uncompacted material sample used for evaluations involving liquid displacement tests. The sealed material sample includes a quantity of uncompacted material forming a material sample which is selected from a larger mixture quantity such that it is representative of the larger mixture""s composition. The sealed sample also includes a preformed resilient bag having a sealed edge portion and a predetermined apparent density value associated therewith. The bag is configured and sized to hold the quantity of uncompacted loose material sample therein. The quantity of loose material sample is sealed within the resilient bag such that a region of the bag proximate to the sealed edge is free of the uncompacted loose material sample. The preformed bag is configured to sealably encase the loose material such that the bag outer walls substantially conform to the sample""s exterior surface contour and prevent the migration of water therein (while the bag remains sealed) during immersion in a liquid water bath. The predetermined apparent density value is used to establish the density of the uncompacted loose material sample.
In a preferred embodiment, during analysis, the sample specimen has a first sealed configuration and a second unsealed configuration. In the sealed configuration, the sample is evacuated of substantially all air therein. Voids are created in the bag resulting from irregularities (coarse, non-congruent or uneven profiles and shapes) of the constituents comprising the sample and the degree of conformance of the evacuated collapsed bag to the sample. The second unsealed configuration is defined by an opening introduced or formed into the sealed bag (the opening introduced therein while the sample and bag are held completely immersed in the liquid bath). During liquid displacement based analysis, the opening destroys the integrity of the sealed encased bag holding the bituminous material sample and allows fluid to enter therethrough to contact the quantity of uncompacted bituminous material (and thus, fill the remaining voids within the bag).
In a preferred embodiment, the uncompacted loose material sample comprises paving mixtures of asphalt and/or a plurality of different types and size aggregates.
Another aspect of the present invention is a vacuum system for preparing and sealing in a pre-formed bag an uncompacted or compacted material specimen for liquid immersion evaluation. The vacuum system comprises a vacuum apparatus with a vacuum receiving chamber having a perimeter defining an internal holding region with a floor. The holding region is configured and sized to receive a preformed bag with a coarse material sample held therein. The vacuum apparatus comprises a sealing ledge located in the vacuum chamber along a perimeter portion thereof. In operation, the sealing ledge is configured to apply heat to and seal an edge of the preformed bag together. The vacuum apparatus also includes an air channel and a vacuum pump in fluid communication with the vacuum chamber. The vacuum apparatus additionally includes a support member positioned or residing on the floor (either directly or indirectly). The support member is configured and sized to hold the specimen in the preformed bag. In operation, the support member is configured and held within the vacuum chamber so that it can translate toward the sealing ledge. As such, the support member is mounted to the vacuum chamber or held therein such that it is substantially free to move in the direction of the sealing means or ledge to help support the weight of the specimen in the bag to inhibit the introduction of punctures or tears during the evacuation or sealing process.
The present method is easily adaptable to specimens having different (increased sizes). This facilitates the laboratory analysis of many different types and sizes of compacted specimens. Indeed, due to the sizes of aggregates used in recent mixtures, it is desirable to increase the size of the specimen undergoing evaluation, whether the specimen is prepared in the laboratory and/or extracted from the field. Typically, the size is increased from conventionally sized specimens having about a 100 mm (4 inch) diameter to specimens having about a 150 mm (6 inch) diameter for different thicknesses.
The present invention also provides methods for determining apparent bag (or other conformable sealant) density with a plurality of different reference specimens of varying size and/or geometry in order to provide improved apparent bag density reference values (more accurately reflecting the behavior of the sealant during specimen measurement). These values can conveniently be predetermined at a production site, saving labor time at the laboratory-testing site. The bag density values are then useable to calculate material density of field material samples measured with sealed bags used according to the present invention. For example, the present invention provides solid reference samples, reference samples with predetermined void configurations formed on the surface thereof, asphalt samples with known void content/thickness, and loose reference samples mixture comprising a plurality of loose non-absorbent articles such as spherical solid material balls (such as marbles), and the like. For the loose reference mixture, a sub-container with water entry ports configured thereon can also be used to hold the loose mixture within the bag (the bag encases the sub-container which holds the mixture).
Advantageously, the present invention provides a reliable and easily used method for determining the maximum specific gravity and/or density of uncompacted or loose bituminous material samples with water displacement evaluation techniques. This technique can also be used to assess asphalt permeability or porosity. Further, unlike conventional test techniques, the methods of the instant invention evacuates the sample in the absence of water and, thus, does not draw water into the vacuum pump during testing procedures.